Graphene-based textile strain sensors were reviewed in terms of their preparation methods, performance, and applications with particular attention on its forming method, the key properties (sensitivity, stability, sensing range and response time), and comparisons. Staple fiber strain sensors, staple and filament strain sensors, nonwoven fabric strain sensors, woven fabric strain sensors and knitted fabric strain sensors were summarized, respectively. (i) In general, graphene-based textile strain sensors can be obtained in two ways. One method is to prepare conductive textiles through spinning and weaving techniques, and the graphene worked as conductive filler. The other method is to deposit graphene-based materials on the surface of textiles, the graphene served as conductive coatings and colorants. (ii) The gauge factor (GF) value of sensor refers to its mechanical and electromechanical properties, which are the key evaluation indicators. We found the absolute value of GF of graphene-based textile strain sensor could be roughly divided into two trends according to its structural changes. Firstly, in the recoverable deformation stage, GF usually decreased with the increase of strain. Secondly, in the unrecoverable deformation stage, GF usually increased with the increase of strain. (iii) The main challenge of graphene-based textile strain sensors was that their application capacity received limited studies. Most of current studies only discussed washability, seldomly involving the impact of other environmental factors, including friction, PH, etc. Based on these developments, this work was done to provide some merit to references and guidelines for the progress of future research on flexible and wearable electronics.
Carbon-based electromagnetic shielding materials are reviewed in terms of their performance, type, and preparation. They include film, composite, foam, and fabric with particular attention on their frequency selectivity ascribed to the periodic structure. The SE/t, referring to shielding effectiveness per unit thickness (dB/mm), and SSE, referring to shielding effectiveness per unit density (dB·cm3/g), are summarized. The main conclusions of this work are as follows: (1) large area film shows higher SE/t, in which carbon nanotube (CNT) film is endowed with the most attractive value (19,500 dB/mm); materials containing CNTs achieve higher shielding efficiency, ascribe to a high specific surface area, have a greater length–diameter ratio, and a one-dimensional continuous-oriented structure; (2) notably, frequency selectivity based on varied period structures has been widely studied; the method includes multilayer structure/printing/cutting/backfilling and, especially, woven fabric; (3) favorable shielding effectiveness is attributed to the shielding material's intrinsic electrical conductivity and structural integrity. Based on these developments, this paper aims to provide some valuable data, highlight the important research direction, and advance the development of carbon-based electromagnetic shielding materials.
The integration of high conductive networks and textiles has become a favorable technical route to fulfill the objectives of wearable electronics. Herein, high stretchable and recoverable PET fabric coated with a layer of silver nanowire network by a simple and scalable polyol-method is provided. The electrothermal performance, resistance temperature-sensitivity, electromagnetic shielding performance, strain sensing, and washability of silver nanowire (AgNWs)/PET fabrics with different coating times were performed. The conductivity of the fabric coated AgNWs of 2.8 mg/cm2 is as high as 175 S/m, the EMI shielding effectiveness is 37 dB, and it gives a highly sensitive strain response to human movement (gauge factor of −6.16 under 10% strain) and an underwater oil repellent angle of 125°. The heating temperature can reach above 100°C within 27 s under an applied current of 0.10 A. In addition, an excellent linearity of the resistance temperature-sensitive behavior for AgNWs/PET fabrics is obtained, and fabric Ag-5 gives a negative temperature coefficient of resistance (TCR) of −0.05%/°C. Knitted fabric with multi-function is obtained by use of silver nanowire coating. This method provides a simple, low-cost and easy-to-scalable process for the production of electronic textiles, such as fabric heater, microwave blocker, sensor, and other technologies.
Electric fabric heaters have demonstrated potential applications in a wide range of fields for medical electrothermal, human healthcare and athletic rehabilitation. Whereas, little attention has been paid to the resistance variations and the interface of electric heaters. Here, this paper focuses on the resistance temperature-sensitive behavior and interfacial electricity of reduced graphene oxide (RGO)/polyester (PET) fabrics, which are obatained through a facile and scalable dip-coating method. When a current of 0.055 ampere (A) is applied, the RGO/PET fabric can achieve an equilibrium temperature about 89 °C in 20 s, with a maximum heating rate of 11.78 °C/s. Besides, the relative resistance changes of RGO/PET fabric are linearly related to the temperature. When the RGO/PET fabric reaches its steady-state temperature of 89 °C, the value of ΔR/R0 drops by ∼30%, showing that the fabric is endowed with temperature sensitivity. These prominent results indicate that the RGO/PET fabric owns great promise in the field of wearable electric heaters. Notably, the contact resistance at the interface of RGO/PET fabric heater is investigated and the mechanism of the temperature in middle part of heater is higher than that of both ends is analyzed. This provides a qualitative decoupling analysis method for the study and analysis of interfacial electricity and electrothermal distribution of carbon materials.
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